Astronomy Archives

June 25, 2009December 24, 2015 by Anne Minard

The Jury Is In: Exploding Stars Really do Pelt us With Cosmic Rays

The rim of RCW 86. Credit: ESO/E. Helder & NASA/Chandra

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Mmm, pretty … and a tad menacing, at least in its explosive past. This is RCW 86, part of a stellar remnant whose explosion was recorded in 185 AD. By studying the remnant in detail, a team of astronomers has been able to nail down the source of cosmic rays that bombard Earth.

During the Apollo flights 40 years ago, astronauts reported seeing odd flashes of light, visible even with their eyes closed. We have since learned that the cause was cosmic rays — extremely energetic particles from outside the Solar System arriving at the Earth, and constantly bombarding its atmosphere. Once they reach Earth, they still have enough energy to cause glitches in electronic components.

Galactic cosmic rays come from sources inside our home galaxy, the Milky Way, and consist mostly of protons moving at close to the speed of light, the “ultimate speed limit” in the Universe. These protons have been accelerated to energies exceeding by far the energies that even CERN’s Large Hadron Collider will be able to achieve.

“It has long been thought that the super-accelerators that produce these cosmic rays in the Milky Way are the expanding envelopes created by exploded stars, but our observations reveal the smoking gun that proves it,” says Eveline Helder from Utrecht University in the Netherlands, the first author of the new study in this week’s Science Express.

“You could even say that we have now confirmed the caliber of the gun used to accelerate cosmic rays to their tremendous energies,” adds collaborator Jacco Vink, also from the Astronomical Institute Utrecht.

For the first time Helder, Vink and colleagues have come up with a measurement that solves the long-standing astronomical quandary of whether or not stellar explosions produce enough accelerated particles to explain the number of cosmic rays that hit the Earth’s atmosphere. The team’s study indicates that they indeed do and directly tells us how much energy is removed from the shocked gas in the stellar explosion and used to accelerate particles.

“When a star explodes in what we call a supernova a large part of the explosion energy is used for accelerating some particles up to extremely high energies,” says Helder. “The energy that is used for particle acceleration is at the expense of heating the gas, which is therefore much colder than theory predicts.”

The researchers looked at the remnant of a star that exploded in AD 185, as recorded by Chinese astronomers. RCW 86, is located about 8,200 light-years away towards the constellation of Circinus (the Drawing Compass). It is probably the oldest record of the explosion of a star.

Using ESO’s Very Large Telescope, the team measured the temperature of the gas right behind the shock wave created by the stellar explosion. They measured the speed of the shock wave as well, using images taken with NASA’s X-ray Observatory Chandra three years apart. They found it to be moving AT between 1 and 3 percent the speed of light.

The temperature of the gas turned out to be 30 million degrees Celsius. This is quite hot compared to everyday standards, but much lower than expected, given the measured shock wave’s velocity. This should have heated the gas up to at least half a billion degrees.

“The missing energy is what drives the cosmic rays,” concludes Vink.

More about the lead image: North is toward the top right and east to the top left. The image is about 6 arc minutes across. Credit: ESO/E. Helder & NASA/Chandra

Source: ESO

June 24, 2009December 24, 2015 by Fraser Cain

Does Mercury Have Rings?

Mercury's limb. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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Think about the planets in the Solar System; Saturn has rings, so do Jupiter, Uranus and Neptune. So what about Mercury? Does planet Mercury have rings?

Sorry, Mercury doesn’t have rings right now. I say right now, because it’s possible that Mercury has had rings in the past, and it could have them again in the future.

There are two ways that scientists think a planet can get rings. The first is the icy rings around Saturn, Jupiter, Uranus and Neptune. Scientists think that Saturn’s rings come from an icy object or moon that was crushed under Saturn’s gravity, becoming its rings. It’s also possible that the ring material just formed in place back when the Solar System formed. We also know that some of Saturn’s moons, like Enceladus, are continuing to spew fresh material into the rings.

Unfortunately, Mercury could never get rings like this. That’s because it’s too close to the Sun. The powerful solar winds blast out from the Sun, and would melt and destroy any icy rings around Mercury. In fact, ice can’t exist closer to the Sun than the asteroid belt, unless it’s hidden in shadow, or protected by an atmosphere like we have on Earth.

The second way for a ring to form is for an asteroid or moon to get too close to a planet and be torn apart by gravity. For a few million years this crushed asteroid would appear as a ring around Mercury, until the chunks finally fell down onto the planet. Astronomers predict that the Martian moon Phobos will eventually suffer this fate, be torn apart by Mars’ gravity, and form a ring for a while.

Mercury doesn’t have any moons, and there aren’t many asteroids that might interact with it, so it might never get a ring – but maybe one day. One thing’s for sure, though, there are no Mercury rings today.

How many rings does Mercury have? Zero.

We have written many stories about rings here on Universe Today. Here’s an article about the Martian moon Phobos might only have 10 million years to live, and here’s an article about what Saturn’s rings are made of.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Mercurio no tiene anillos?

Reference:
NASA Science for Kids

June 24, 2009December 12, 2019 by Abby Cessna

What are The Outer Planets of the Solar System?

The Jovian planets of the Solar System. Credit: bork.hampshire.edu

Astronomers have divided the eight planets of our solar system into the inner planets and the outer planets. The 4 inner planets are the closest to the Sun, and the outer planets are the other four – Jupiter, Saturn, Uranus, and Neptune. The outer planets are also called the Jovian planets or gas giants. Like the inner planets, the outer planets have similar characteristics to one another.

The outer planets are so much larger than the inner planets that they make up 99 percent of the mass of the celestial bodies that orbit the Sun. Although mainly composed of gas, the outer planets also have other ingredients. Somewhere at the center is what scientist refer to as a rocky core, although it is actually composed of liquid heavy metals. While the inner planets have few or no moons, the outer planets have dozens each. The inner and outer planets are separated by the asteroid belt.

Jupiter is the largest planet in our Solar System with a mass more than three hundred times Earth’s mass. Jupiter is not only the largest planet, it also has the most moons – 63 identified so far. Jupiter is one of the brightest objects in the sky and has a very stormy atmosphere. One major storm, the Great Red Spot, is as big as the Earth.

Saturn is hard to miss with its distinctive, large rings. Although all of the outer planets have rings, Saturn’s are the most visible ones. Astronomers did not know that there any other planets with rings until 1977 when Uranus’ rings were discovered. Soon after that, astronomers discovered rings around both Jupiter and Neptune.

Uranus has the smallest mass of the outer planets, although in size it’s a little bigger than Neptune. It is the only planet to rotate on its side. Scientists are unsure why it rotates that way, although there are a couple theories. One suggests it suffered a major collision and another hypothesizes that smaller shifts during the planets’ formation caused its unusual rotation.

Neptune is the final outer planet in the solar system. Neptune’s winds are the fastest of any planets in the Solar System and can reach more than 1,200 miles per hour. While all of the outer planets’ atmospheres contain hydrogen and helium, Neptune and Uranus contain significant amounts of what astronomers call ices. These ices include water, ammonia, and methane. The methane in Neptune and Uranus is what gives the planets their blue color.

Check out these other articles from Universe Today on the outer solar system and the inner solar system.

If you are searching for more information, NASA has many articles, including one on the planets and Science Daily is also a rich resource for information on the outer planets.

Astronomy Cast has a number of episodes on the Jovian planets including this one on Jupiter.

June 24, 2009December 24, 2015 by Anne Minard

Mysterious “Blobs” Are Windows Into Galaxy Formation

Credit: Left panel: X-ray (NASA/CXC/Durham Univ./D.Alexander et al.); Optical (NASA/ESA/STScI/IoA/S.Chapman et al.); Lyman-alpha Optical (NAOJ/Subaru/Tohoku Univ./T.Hayashino et al.); Infrared (NASA/JPL-Caltech/Durham Univ./J.Geach et al.); Right, Illustration: NASA/CXC/M.Weiss

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Astronomers say they’ve discovered the “coming of age” of galaxies and black holes, thanks to new data from NASA’s Chandra X-ray Observatory and other telescopes. The new discovery helps resolve the true nature of gigantic blobs of gas observed around very young galaxies, and sheds light on the formation of galaxies and black holes.

The findings, led by Jim Geach of Durham University in the UK, will appear in the July 10 issue of The Astrophysical Journal.

About a decade ago, astronomers discovered immense reservoirs of hydrogen gas — which they named “blobs” – while conducting surveys of young distant galaxies. The blobs are glowing brightly in optical light, but the source of immense energy required to power this glow and the nature of these objects were unclear.

Based on the new data and theoretical arguments, Geach and his colleagues show that heating of gas by growing supermassive black holes and bursts of star formation, rather than cooling of gas, most likely powers the blobs. The implication is that blobs represent a stage when the galaxies and black holes are just starting to switch off their rapid growth because of these heating processes. This is a crucial stage of the evolution of galaxies and black holes – known as “feedback” – and one that astronomers have long been trying to understand.

“We’re seeing signs that the galaxies and black holes inside these blobs are coming of age and are now pushing back on the infalling gas to prevent further growth,” said coauthor Bret Lehmer, also of Durham. “Massive galaxies must go through a stage like this or they would form too many stars and so end up ridiculously large by the present day.”

Chandra and a collection of other telescopes including Spitzer have observed 29 blobs in one large field in the sky dubbed “SSA22.” These blobs, which are several hundred thousand light years across, are seen when the Universe is only about two billion years old, or roughly 15 percent of its current age.

In five of these blobs, the Chandra data revealed the telltale signature of growing supermassive black holes – a point-like source with luminous X-ray emission. These giant black holes are thought to reside at the centers of most galaxies today, including our own. Another three of the blobs in this field show possible evidence for such black holes. Based on further observations, including Spitzer data, the research team was able to determine that several of these galaxies are also dominated by remarkable levels of star formation.

The radiation and powerful outflows from these black holes and bursts of star formation are, according to calculations, powerful enough to light up the hydrogen gas in the blobs they inhabit. In the cases where the signatures of these black holes were not detected, the blobs are generally fainter. The authors show that black holes bright enough to power these blobs would be too dim to be detected given the length of the Chandra observations.

Besides explaining the power source of the blobs, these results help explain their future. Under the heating scenario, the gas in the blobs will not cool down to form stars but will add to the hot gas found between galaxies. SSA22 itself could evolve into a massive galaxy cluster.

“In the beginning the blobs would have fed their galaxies, but what we see now are more like leftovers,” said Geach. “This means we’ll have to look even further back in time to catch galaxies and black holes in the act of forming from blobs.”

Sources/more information: the Chandra sites at Harvard and NASA.

June 23, 2009April 26, 2016 by Nancy Atkinson

Gemini VI

This photograph of the Gemini 7 spacecraft was taken from the hatch window of the Gemini 6 spacecraft during rendezvous and station keeping maneuvers at an altitude of approximately 160 miles on December 15, 1965. Credit: NASA

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Gemini VI ended up launching after Gemini VII, making it the fifth manned mission of Project Gemini. The astronauts on board were Walter M. Schirra Jr., Commander and Thomas P. Stafford, Pilot.

The mission launched on Dec. 15, 1965 at 8:37 am EST, and the two-man capsule reached at altitude of 311.3km. The crew made 16 orbits and their flight lasted 1 Day, 1 hour, 51 min, 24 seconds.

The crew of Gemini VI, Stafford and Schirra. Credit: NASA

The original flight plan called for the Gemini VI to rendezvous with an Agena target vehicle in space to test out rendezvous and docking procedures. However the Agena launched on October 25 blew up on the way to orbit. After much discussion, NASA decided to launch Gemini VII first and have Gemini VI rendezvous the Gemini VII spacecraft. This required a quick one week turnaround of the launch pad, something NASA had never done before.

Gemini VII launched on Dec. 4, 1965 but the first launch attempt for Gemini VI on Dec. 12 was aborted, as the Titan II rocket ignited and then shut down a second later. As commander, Schirra had the option of ejecting the crew to safety, but he waited it out and did not pull the abort handles. That decision allowed a quick second launch attempt on Dec. 15 that went perfectly.

The primary objective was to rendezvous with Gemini-VII, which was accomplished successfully, making it the first manned rendezvous controlled entirely by the self-contained, on-board guidance, control, and navigation system. This system provided the crew of Gemini 6 with attitude, thrusting, and time information needed for them to control the spacecraft during the rendezvous. The two spacecraft came within 16 meters.

Secondary objectives were to stationkeep with Gemini VII, conduct visibility tests for rendezvous and evaluate reentry guidance capability. The crew had three planned experiments, but the Radiation in Spacecraft experiment was unable to be done because stationkeeping with Gemini VII interfered with it.

Gemini VI splashed down on December 16, 1965, landing at 23 degrees 35 minutes North and 67 degrees 50 minutes West, missing its target landing location by only 12.9 km. The crew was recovered by the USS Wasp, which had the crew onboard in 66 minutes.

NASA’s Gemini VI history page.

More images from Gemini VI.

June 23, 2009December 24, 2015 by Aalla

Continental Drift Theory

In elementary school, every teacher had one of those pull-down maps of the world to teach geography. On occasion, I thought the largest land masses, known as continents, reminded me of pieces in a jigsaw puzzle. They just seemed like they should fit together, somehow. Not until I took Earth Science, in 8TH grade, did I discover my earlier idea was correct. My teacher explained about a phenomenon, known as, The Continental Drift Theory. He said that some German had the same idea I did.

The man my teacher mentioned, Alfred Wegener (Vay gen ner), developed The Continental Drift Theory in 1915. He was a meteorolgist and a geologist. His theory basically said that, at one time, there existed one large supercontinent, called, Pangea, pan, meaning all-encompassing, and, gea, meaning the Earth. He went on to suggest that, seismic activity, such as erthquakes, volcanic eruptions, and tsunamis, also called tidal waves, eventually created fissures, or cracks in the Earth. As these fissures became larger, longer, and deeper, 7 pieces of Pangea broke off and, over time, drifted to the places where they are now. These 7 large pieces of land are what we now call, continents. They are: North America; South America; Europe; Asia; Africa; Antarctica; and, Australia. Some people refer to the country as Australia, and the continent as, Oceania. They do this because there are other countries, such as New Zealand, included as a part of that particular continent.

At the time, people thought Wegener was, well, “nuts.” Only in the 1950s did people begin to take his idea seriously. According to the United States Geological Survey (the USGS), thanks to the use of the submarine and the technology developed during World War II, scientists learned a lot about the Ocean Floor. When they found out that it was not as old as the Crust, or Surface, of the Earth, sicentists had to ask themselves, “Why?”

The answers have to do with earthquakes, volcanoes, and magnetism. When the Earth cracks, molten magma, from the middle of the Earth, known as the Mantle, works its way to the surface, where it becomes known as, lava. That lava melts away some of the older layers; then, when the water cools that lava, it forms a new layer of Earth. For that reason, if scientists tried to determine the age of the Earth from samples taken from the Ocean Floor, they would be very wrong.

That same equipment also helped scientists recognize that heavy amounts of basalt, a volcanic rock that contains high amounts of iron, could throw compasses off course. This information provided one more pieces to the puzzle. Now, scientists recognize that the North and South Poles were not always where they currently are.

The Earth changes every day. Although we might not notice it, the continents move all the time. We don’t only revolve, or spin, around the Sun. We also drift across the surface of the planet.

The United States Geological Survey has some excellent information on this topic.

University Today has some other fabulous material about this and related topics, including Earth, Barely Habitable?, by Fraser Cain begin_of_the_skype_highlighting end_of_the_skype_highlighting, and Interesting Facts About Planet Earth.

You can also read or listen to Episode 51: Earth, of Astronomy Cast, also produced by Universe Today.

Sources:
http://en.wikipedia.org/wiki/Continental_drift
http://www.ucmp.berkeley.edu/history/wegener.html
http://pubs.usgs.gov/gip/dynamic/historical.html

June 22, 2009April 26, 2016 by Nancy Atkinson

Gemini IV

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The second mission of Project Gemini was Gemini IV. The mission launched on June 3, 1965 at 10:15 am local time, from Cape Canaveral in Florida. The two astronauts on board were James A. McDivit, Commander and Edward H. White II, Pilot.

A Titan rocket boosted the Gemini capsule to an altitude of 296.1 km. McDivit and White made 62 orbits, and the duration of their flight was 4 Days, 1 hour, 56 min, 12 seconds. The Gemini spacecraft weighed 3574kg.

The highlight of the mission was an EVA (extra vehicular activity) by Ed White, where he climbed out of the spacecraft and while tethered, floated for 23 minutes, not nearly long enough for White. He later said the spacewalk was the most comfortable part of the mission, and said the order to end it was the “saddest moment” of his life.

White was attached to the capsule by a 25 foot umbilical cord. He initially used a gas powered gun held in his hand to maneuver. After the first three minutes the fuel ran out and White moved around by twisting his body and pulling on the cord.

The other main objectives of the mission were to evaluate the effects of prolonged space flight which included checking out the performance of a spacecraft during a four-day mission, and evaluating the procedures for crew rest and work cycles, eating schedules, and realtime flight planning.

Secondary objectives included attempting to stationkeep and rendezvous with second stage of Gemini Launch Vehicle and perform 11 experiments.

All the primary objectives were achieved except one: computer controlled reentry was not able to be used because of inadvertent alteration of computer memory. All secondary objectives were met except that due to excess fuel consumption, all the stationkeeping and rendezvous maneuvers were not able to be done.

Gemini IV splashed down in the Atlantic Ocean on June 7, 1965 27 degrees 44 minutes North and 74 degrees 11minutes West, about 81.4km from attempted landing zone.

More images from Gemini IV

NASA’s history page on Gemini IV

June 22, 2009April 26, 2016 by Abby Cessna

Life on Other Planets

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For centuries, men have pondered the possibility of life on other planets and tried to prove its existence. Even before the first shuttle or probe was launched, stories of life on other planets and life invading our own planet, were published prolifically. Whether it’s a desire to connect with others or a burning curiosity to know whether we are truly alone, the question of life on other planets fascinates people from every walk of life.

An article on extraterrestrial life would not be complete without discussing Mars. Mars has been the biggest focus of the ongoing search for life on other planets for decades. This is not just a wild assumption or fancy; there are several reasons why scientists consider Mars the best place to look for extraterrestrial life. One reason why many people, including scientists, look to Mars as a possible source of life is because they believe there may be water on the planet. Since the telescope was first invented, astronomers have been able to see the channels in the terrain that look like canals or canyons. Finding water on a planet is vitally important to proving that life exists there because it acts as a solvent in chemical reactions for carbon-based life.

Another reason astronomers consider Mars as a likely location for life is because there is a good possibility that Mars is in the habitable zone. The habitable zone is a theoretical band of space a certain distance from the Sun in which conditions are optimal for the existence of carbon-based life. Unsurprisingly, Earth is in the middle of the habitable zone. Although astronomers do not know how far this zone could extend, some think that Mars could be in it.

Most astronomers are looking for life that is carbon-based and similar to life on Earth. For instance, the habitable zone only applies to favorable conditions for supporting carbon-based life, and it is definitely possible for forms of life that do not need water to exist.

Astronomers do not limit themselves to our Solar System either, suggesting that we should look at different solar systems. Scientists are planning to use interferometry–an investigative technique that implements lasers, which is used in astronomy as well as other fields– to find planets in the habitable zones of other solar systems. Astronomers believe that there are hundreds of solar systems and thousands of planets, which means that statistically the odds are favorable for finding another planet that supports life. While NASA develops better probes, the search for life continues.

There are a number of sites with more information including life on other planets from Groninger Kapteyn Institute astronomy students and NASA predicts non-green plants on other planets from NASA.

Universe Today has a number of articles concerning life on other planets including searching for life on non-Earth like planets and single species ecosystem gives hope for life on other planets.

Take a look at this podcast from Astronomy Cast on the search for water on Mars.

June 22, 2009December 24, 2015 by Tammy Plotner

The Trouble With Trifids

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Almost everyone who is familiar with space images has seen this beautiful and color emission and reflection nebula – but take a really close look. This isn’t a Hubble image. It was done with a ground based camera!

When looking at M20 through a telescope, what you will see won’t match the photo above, while what is normally presented in science journals is colorful. Why? Well, when it comes to photographs, exposure times and wavelengths causes the different colors you see. Photographically, the red emission nebula contained within Messier 20 has a bright blue star cluster in it central portion. It glows red because the ultraviolet light of the stars ionizes the hydrogen gas, which then recombines and emits the characteristic red hydrogen-alpha light captured on film. Further away, the radiation from these hot, young stars becomes too weak to ionize the hydrogen. Now the gas and dust glows blue by reflection!

Of course, there are other ways of looking at Messier objects, too. It was my great fortune on Saturday night to have an opportunity to study M20 through an image intensifier – a highly complex piece of equipment which uses x-rays and produces a ‘live’ image feed which is displayed on a binocular like eyepiece screen. I cannot even begin to describe to you what this does to observing, except to say that it opens a dimension to to eyes never before experienced. No matter how it is observed, the Trifid – or “three lobed” nebula has a distinctive set of dark dust lanes which divide it. These also have a classification of their own and were cataloged by E.E. Barnard as dark nebula Barnard 85 (B 85).

In 1999 the Hubble Space Telescope took this photograph – a look deep into the Trifid nebula at some of its star forming regions and found a stellar jet poking its way into the cloud, like a fabulous twisted antenna. Inside the exhaust column is a new star waiting to be born, yet sometime over the next 10,000 years the central massive star will probably erode away all of its material before it can fully form. Nearby a stalk stands waiting… Like the jet, it is also a stellar nursery – one with an EGG (evaporating gaseous globule) at its tip – a condensed cloud of gas able to survive so far. “If our interpretation is correct, the microjet may be the last gasp from a star that was cut off from its supply lines 100,000 years ago.” says Jeff Hester of the Department of Physics & Astronomy, “The vast majority of stars like our sun form not in isolation, but in the neighborhood of massive, powerful stars. HST observations of the Trifid Nebula provide a window on the nature of star formation in the vicinity of massive stars, as well as a spectacular snapshot of the “ecology” from which stars like our sun emerge.”

But, is it possible for those of us here on the ground to perform our own deep studies of regions of space like the Trifid Nebula? The answer is yes. Take a look at this small frame clipped from the full sized image you see above. While the colors haven’t been processed the same, those EGGs are there!

It’s a cinch that those of us that don’t have a multitude of titles behind our names are ever going to be allowed Hubble time… even at this late stage of the game. You know our findings will never be placed in the hallowed journals of science. But, why should the scientists be allowed to have all the fun? While images like Eddie’s might be considered “amateur”, it is anything but. While he’s chosen to reveal it in an artistic format, you must stop to think about how much information has been collected inside of his raw data. Unlike a simple film photograph, CCD imaging gathers huge amounts of information that’s processed out by what data is desired. “Velocity maps of the inner regions of the bright H II regions NGC 6514 were made with unprecedented spatial and spectral resolution in the 5007 A line of forbidden O III. In addition to the advantages of an instrumental full width at half-maximum intensity of only 5.4 km/s, the small thermal width of the heavy oxygen ion also allows determination of accurate line widths and velocities.” says C.R. O’Dell (et al), “The CCD spectra were numerically fitted to Gaussian line profiles and revealed two separate velocity systems in NGC 6523. The data sets of radial velocities were used to derive the dependence of the most probable turbulent velocities upon the sample sizes, and the spatial dependence of the structure function. These relationships are the basic functions for comparison with the predictions of the models for turbulence in H II regions.”

To me, one of the most fascinating aspects of Mr. Trimarchi’s picture wasn’t so much the huge revelation of all the Herbig-Haro objects – but a tiny, fine detail that you probably took for granted when you looked at it. Dust extinction… There’s a lot of very exiting things in that photograph, but there’s a detail he left in there that most other photographers filter out! The studies of C.R. O’Dell taught me to take a much closer look a certain properties in astrophotos, because I might see something that others missed, and in this case its a huge amount of dust extinction which he proved to exist around M20 many, many years ago. (Like back when my telescopes still had training wheels.)

Why are things like that important? In this circumstance, knowing there was more dust there than should have been lead to further investigations – and those in turn led to a discovery: “We report the discovery of a new candidate barrel-shaped supernova remnant (SNR) lying adjacent to M20 and two shell-type features to the north and east of SNR W28.” says F. Yusef-Zadeh (et al), ” Future observations should clarify whether the nonthermal shell fragment is either part of W20 or yet another previously unidentified shell-type SNR.”

Keep those cameras rolling… Who knows what we may find tomorrow?

Many thanks to Eddie Trimarchi of Southern Galactic for sharing this wonderul image with us!

June 19, 2009December 24, 2015 by Fraser Cain

Yellowstone Eruption

Welded tuff at Yellowstone National Park.

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Millions of people visit Yellowstone National Park every year, but how many think about the fact that they’re standing on top of one of the largest volcano calderas on Earth? Within the last 17 million years, there have been more than 100 large eruptions within the Yellowstone caldera, and thousands of smaller lava flows and steam explosions. In fact, the last great Yellowstone eruption happened about 70,000 years ago, and it only seems like a matter of time before it all happens again. Don’t panic, though, geologists monitor Yellowstone carefully, and they don’t think any large eruptions will happen soon.

The Yellowstone calderas measures 55 km wide by 72 km long, and rises to an elevation of 3,142 meters at its tallest point – Mount Sheridan. The constant uprise of the region created a plateau where there used to be a mountain range. These eruptions and uplift helped create the eastern Snake River Plain.

In the last 17 million years, there have been 142 caldera-forming eruptions in Yellowstone. This is an eruption large enough that a significant amount of lava, ash or rock were released – usually as an explosive eruption. Three of these eruptions have been classified as “super eruptions”, where up to 2,500 cubic km of ash and rock exploded out of the volcano. Just for comparison, Mount St. Helens, which erupted in 1980, only released 1 cubic km of material… so 2,500 times that in a single eruption. One of these super eruptions would have devastated most of North America, and cooled the climate of planet Earth for decades. The oldest of these Yellowstone eruptions happened 2.1 million years ago, which created the Huckleberry Ridge Tuff. The next oldest happened 1.3 million years ago, and the most recent super eruption happened about 640,000 years ago.

And since that last super eruption, there have been numerous smaller (but still powerful eruptions) non-explosive eruptions. The most recent lava flow has been estimated to have occurred about 70,000 years ago, and a steam explosion created a 5-km crater 13,800 years ago. The only eruptions that happen at Yellowstone today are the numerous geothermal vents around the caldera. These mix with water to create the famous geysers, like Old Faithful. These geysers indicate that Yellowstone is still a very active region, and more eruptions are likely.

Geologists are continuing to monitor the Yellowstone caldera, including the speed at this the caldera floor is rising up. Like Hawaii, Yellowstone is created by a single volcanic hotspot located under the Earth. The North American Plate is slowly moving over top of the hotspot, creating a long chain of calderas. The current caldera in Wyoming is the current location of the hotspot. Geologists have measured that the caldera floor is rising upwards at almost 7 cm per year. Fortunately, they find no evidence that we’re due for another super Yellowstone eruption. Of course, these things are difficult to predict.

We have written many articles about volcanoes for Universe Today. Here’s an article about about a Yellowstone-like formation on Mars, and an article about how extreme life in Yellowstone might offer hope for the search for life on Mars.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Source: Wikipedia